As is well-known, a sheet such as a long resin film or paper sheet which is continuously manufactured is normally rolled around a roll core into a roll shape and accommodated. In a sheet roll which accommodates the sheet in this manner, when the sheet rolled around the roll core does not satisfy a predetermined length, there are cases where a method is employed in which the sheet is kept rolled around the roll core while the leading end of another sheet is coupled to the terminal end of the sheet which is already rolled around the roll core until the entire length of the sheet reaches the predetermined length (see, e.g., Patent Document 1).
In addition, in recent years, there is developed a glass film which is reduced in thickness into a film form and, similarly to the above-mentioned sheet such as the resin film or the like, there is a growing use of a form in which the continuously manufactured long glass film is rolled around the roll core into the roll shape and accommodated (see, e.g., Patent Document 2). In this case as well, when the glass film rolled around the roll core does not satisfy the predetermined length, there are cases where the method is employed in which the leading end of another glass film is coupled to the terminal end of the glass film which is already rolled around the roll core to extend the entire length of the glass film.
In addition, there are cases where predetermined processing (e.g., washing, film formation, cutting or the like) is performed on the above-mentioned sheet roll according to what is called a Roll to Roll process. When the sheet is a brittle material such as the glass film or the like, for the purpose of preventing the breakage of the sheet made of the brittle material, there are cases where the end portion of a sheet made of a tough material such as a resin sheet or the like (in this case, the sheet is referred to as, e.g., a leader) is coupled to the end portion of the sheet made of the brittle material, and the entire sheet is guided into a device which executes the Roll to Roll process by using the terminal end of the sheet made of the tough material as the lead.
Consequently, in the sheet roll, as in the former, there are cases where the sheets of the same type are coupled together, or, as in the latter, there are cases where the sheets of different types are coupled together.